Abstract
Abundances of a range of air pollutants can be inferred from satellite UV-Vis spectroscopy measurements by using the unique absorption signatures of gas species. Here, we implemented several spectral fitting methods to retrieve tropospheric NO2, SO2, and HCHO from the ozone monitoring instrument (OMI), with radiative simulations providing necessary information on the interactions of scattered solar light within the atmosphere. We analyzed the spatial distribution and temporal trends of satellite-observed air pollutants over eastern China during 2005–2017, especially in heavily polluted regions. We found significant decreasing trends in NO2 and SO2 since 2011 over most regions, despite varying temporal features and turning points. In contrast, an overall increasing trend was identified for tropospheric HCHO over these regions in recent years. Furthermore, generalized additive models were implemented to understand the driving forces of air quality trends in China and assess the effectiveness of emission controls. Our results indicated that although meteorological parameters, such as wind, water vapor, solar radiation and temperature, mainly dominated the day-to-day and seasonal fluctuations in air pollutants, anthropogenic emissions played a unique role in the long-term variation in the ambient concentrations of NO2, SO2, and HCHO in the past 13 years. Generally, recent declines in NO2 and SO2 could be attributed to emission reductions due to effective air quality policies, and the opposite trends in HCHO may urge the need to control anthropogenic volatile organic compound (VOC) emissions.
Highlights
Nitrogen dioxides (NO2), sulfate dioxides (SO2), and formaldehyde (HCHO) are short-lived and reactive trace gases that play important roles in atmospheric chemistry and air pollution[1]
HCHO usually originates from the photochemical reactions of volatile organic compounds (VOCs) and can be used as a Correspondence: Cheng Liu or Qihou Hu or Zhaonan Cai 1School of Earth and Space Sciences, University of Science and Technology of China, 230026 Hefei, China 2Department of Precision Machinery and Precision Instrumentation, University of Science and Technology of China, 230026 Hefei, China Full list of author information is available at the end of the article
There still remain a series of unanswered questions, e.g., the separation of meteorological effects from the human-induced variations in air pollution and the evaluation of the effectiveness of emission control measures or air quality policies implemented by the Chinese government, such as the Air Pollution Prevention and Control Action Plan (APPCAP) issued in 201323
Summary
Nitrogen dioxides (NO2), sulfate dioxides (SO2), and formaldehyde (HCHO) are short-lived and reactive trace gases that play important roles in atmospheric chemistry and air pollution[1]. Monitoring Instrument (OMI)[12], and Global Ozone Monitoring Experiment–2 (GOME-2)[13,14], have achieved the global monitoring of atmospheric trace gases, including NO2, SO2, HCHO, and O3, by using their unique absorption signatures in a shorter wavelength range (250–500 nm). The role of emissions and meteorological conditions in the evolution of air pollution has been investigated for cases such as heavy pollution episodes in winter in Beijing[19] and several important international events during which the government has conducted strict emission controls in Beijing and Nanjing[20,21,22]. There still remain a series of unanswered questions, e.g., the separation of meteorological effects from the human-induced variations in air pollution and the evaluation of the effectiveness of emission control measures or air quality policies implemented by the Chinese government, such as the Air Pollution Prevention and Control Action Plan (APPCAP) issued in 201323
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